1. Field of the Invention
The present invention relates to a method for cleaning a semiconductor wafer and a semiconductor wafer.
2. Description of Related Art
A method for polishing a semiconductor silicon wafer using a polishing slurry, which includes a first polishing step, a second polishing step and a final polishing step, has been traditionally known (for example, see Document 1: JP-2007-73686).
Also, a method for cleaning and removing an oxide film by injecting an aqueous solution containing hydrogen fluoride to the oxide film on a surface of a semiconductor silicon wafer to etch the oxide film has been known (for example, see Document 2: JP-2006-351736).
When foreign substances are mixed in a slurry during the slurry polishing as disclosed in Document 1, stress is locally applied on a surface of a semiconductor wafer to alter the crystal structure of silicon (referred to as altered silicon hereinafter), the altered silicon generating a convex defect. Incidentally, an etching rate using hydrogen fluoride of the altered silicon is higher than that of silicon and lower than that of a silicon oxide film.
To remove such a defect, the method as disclosed in Document 2 is used. However, when the oxide film is etched under a condition capable of removing the altered silicon, only the defect of the altered silicon is removed and a large depressed channel is formed on the surface of the semiconductor wafer because the etching rate of the altered silicon is higher than that of silicon as described above.
Further, when hydrofluoric acid is sprayed, the amount of deposits such as particles adhering to the surface of the semiconductor silicon wafer is increased because hydrofluoric acid contains more impurities than the gas containing hydrogen fluoride.